"In scientific circles, it has been well-recognized that the
Arctic is rapidly changing, certainly faster than any other time
during recorded history," said sea ice physicist Jeremy Wilkinson
at the Scottish Association for Marine Science.

Satellites, while they provide excellent views of the area of
Arctic Ocean covered by sea ice, cannot yet scan ice thickness from space. Researchers
instead rely on scientific instruments such as those that
generate magnetic fields to induce what are called eddy
currents in the water beneath sea ice. The devices can measure
the strength of these currents, which depends on the distance
between the instruments and the bottom of the sea ice, thus
revealing how thick the ice is. They typically are installed
on the bows of icebreaker ships or hung below helicopters.

During time spent with Inuit hunters during research on the sea
ice off Greenland, "we learned of the severe difficulties that
the local communities faced because of the climate-driven changes
to the sea ice conditions," Wilkinson recalled. "We also saw the
large number of dog teams that were on the ice everyday and the
vast distances they covered. Then came the light bulb moment —
why don't we put sensors on these sleds?"

Sled-mounted sensors

These instruments were hard to mount on sleds because they are
unwieldy, consisting of 13-foot-long, 2-inch-wide (4 meters long,
5 centimeters wide) pipes with small boxes of electronics in the
middle. However, researchers have recently developed half-length
versions of the devices that can fit on the sleds of the Inuit,
who routinely hunt and travel over large areas of Arctic sea ice in the course of a
day, sometimes traveling many thousands of miles a
season.

Each instrument was modified to be as autonomous as possible,
making them easy to use. For example, each unit has a GPS device
to record coordinates, a motion sensor that automatically detects
when the sled is moving to activate the system, and solar panels
to keep the batteries charged when the sun is out. All this data
are stored in the instrument and transmitted over satellite in
real time.

"For years, the Inuit have been warning that the sea ice
conditions are changing," Wilkinson said. "However, much of their
observations are qualitative in nature. These sensors allow them
to make accurate and quantitative measurements that can be more
readily used by the scientific community."

Field testing in Greenland

These sled-mounted devices were tested in the field last May on
the ice on the edges of the coast near Qaanaaq in northwestern
Greenland, with two hunters each
volunteering a sled. To see how accurate these instruments
were, scientists also drilled nearly 150 holes in the ice and
compared findings.

The instruments proved accurate, coming within roughly 1 inch
(2.8 cm) of drilling results. They also gathered data across
almost 125 miles (200 km) in just two days, corresponding to
about 20,000 independent ice thickness measurements.

The Inuit hunters gave welcome advice on where and how to mount
the instruments and what modifications were needed to withstand
rigorous daily use. They were also enthusiastic about helping
monitor ice conditions.

"Changes in the thickness, stability and length of the sea ice
season will not only influence global climate but will also
impact severely on the lives of the Inuit, who rely on the ice
not only as their winter highway — faster and safer than the sea
in summer — but also as an important access route for hunting,"
Wilkinson said.

The researchers seek to further improve the instruments,
recording air pressure and adding on better solar panels. The
next deployment is set for February to June of 2011.

"The synergy of traditional techniques with cutting-edge
technology will enable better information on ice thickness to be
obtained in real time," Wilkinson said. "This in turn will lead
better and more accurate sea ice charts to be derived and
delivered to the local community."